Method and apparatus for providing cell re-selection

ABSTRACT

An approach is provided for cell re-selection. A notification message is generated to indicate initiation of a coverage area re-selection procedure to operate in a new coverage area from a current coverage area. The re-selection procedure is performed if an acknowledgement message is received in response to the notification message.

RELATED APPLICATIONS

This application claims the benefit of the earlier filing date under 35U.S.C. §119(e) of U.S. Provisional Application Ser. No. 60/985,537 filedNov. 5, 2007, entitled “Method and Apparatus for Providing CellRe-selection,” the entirety of which is incorporated herein byreference.

BACKGROUND

Radio communication systems, such as wireless data networks (e.g., ThirdGeneration Partnership Project (3GPP) Long Term Evolution (LTE) systems,spread spectrum systems (such as Code Division Multiple Access (CDMA)networks), Time Division Multiple Access (TDMA) networks, WiMAX(Worldwide Interoperability for Microwave Access), etc.), provide userswith the convenience of mobility along with a rich set of services andfeatures. This convenience has spawned significant adoption by an evergrowing number of consumers as an accepted mode of communication forbusiness and personal uses. To promote greater adoption, thetelecommunication industry, from manufacturers to service providers, hasagreed at great expense and effort to develop standards forcommunication protocols that underlie the various services and features.One area of effort involves cell re-selection when a mobile device movesfrom one cell to another cell. Traditionally, such movement involvesunnecessarily reserving network resources—i.e., wasting networkcapacity.

SOME EXEMPLARY EMBODIMENTS

Therefore, there is a need for an approach for providing an efficientcell re-selection procedure, in the context of existing and developingstandards.

According to one embodiment of the invention, a method comprisesgenerating a notification message indicating initiation of a coveragearea re-selection procedure to operate in a new coverage area from acurrent coverage area. The method also comprises performing there-selection procedure in response to the notification message.

According to another embodiment of the invention, a computer-readablestorage medium carries one or more sequences of one or more instructionswhich, when executed by one or more processors, cause the one or moreprocessors to perform a method comprising generating a notificationmessage indicating initiation of a coverage area re-selection procedureto operate in a new coverage area from a current coverage area. Themethod also comprises performing the re-selection procedure in responseto the notification message.

According to another embodiment of the invention, an apparatus comprisesa re-selection logic configured to generate a notification messageindicating initiation of a coverage area re-selection procedure tooperate in a new coverage area from a current coverage area. There-selection logic is further configured to perform the re-selectionprocedure in response to the notification message.

According to another embodiment of the invention, a method comprisesreceiving a notification message indicating initiation of a coveragearea re-selection procedure to operate in a new coverage area from acurrent coverage area. The method also comprises generating anacknowledgement message to permit executing the re-selection procedurein response to the notification message.

According to another embodiment of the invention, a computer-readablestorage medium carries one or more sequences of one or more instructionswhich, when executed by one or more processors, cause the one or moreprocessors to perform a method comprising receiving a notificationmessage indicating initiation of a coverage area re-selection procedureto operate in a new coverage area from a current coverage area. Themethod also comprises generating an acknowledgement message to permitexecuting the re-selection procedure in response to the notificationmessage.

According to another embodiment of the invention, an apparatus comprisesa re-selection logic configured to receive a notification messageindicating initiation of a coverage area re-selection procedure tooperate in a new coverage area from a current coverage area. There-selection logic is further configured to generate an acknowledgementmessage to permit executing the re-selection procedure in response tothe notification message.

According to another embodiment of the invention, a method comprisesallocating resource to a user equipment. The method also comprisesdetermining whether the user equipment is in a coverage areare-selection state. The method further comprises restricting executionof a coverage area re-selection procedure if the user equipment is in acoverage area re-selection state and is currently assigned withdedicated uplink transmission resources.

According to another embodiment of the invention, a computer-readablestorage medium carries one or more sequences of one or more instructionswhich, when executed by one or more processors, cause the one or moreprocessors to perform a method comprising determining whether the userequipment is in a coverage area re-selection state. The method furthercomprises restricting execution of a coverage area re-selectionprocedure if the user equipment is in a coverage area re-selection stateand is currently assigned with dedicated uplink transmission resources.

According to yet another embodiment of the invention, an apparatuscomprises a resource allocation logic configured to allocate resource toa user equipment, and to determine whether the user equipment is in acoverage area re-selection state. The apparatus also comprises are-selection logic configured to restrict a coverage area re-selectionprocedure if the user equipment is in the coverage area re-selectionstate and is currently assigned with dedicated uplink transmissionresources.

Still other aspects, features, and advantages of the invention arereadily apparent from the following detailed description, simply byillustrating a number of particular embodiments and implementations,including the best mode contemplated for carrying out the invention. Theinvention is also capable of other and different embodiments, and itsseveral details can be modified in various obvious respects, all withoutdeparting from the spirit and scope of the invention. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention are illustrated by way of example, andnot by way of limitation, in the figures of the accompanying drawings:

FIG. 1 is a diagram of a communication system capable of providingefficient cell re-selection process, according to an exemplaryembodiment;

FIGS. 2A and 2B are flowcharts of a coverage area re-selection processinvolving signaling of movement from a current coverage area to a newcoverage area, according to various exemplary embodiments;

FIG. 3 is a flowchart of a process for temporarily disabling a coveragearea re-selection procedure, according to an exemplary embodiment;

FIG. 4 is a diagram of an exemplary high speed random access channel(HS-RACH) procedure for supporting cell-re-selection, according tovarious exemplary embodiments;

FIG. 5 is a diagram showing usage of Enhanced Dedicated Channel (E-DCH)as a RACH shared channel, according to various exemplary embodiments;

FIGS. 6 and 7 are diagrams of simulation results relating to HS-RACHcapacity, according to various exemplary embodiments;

FIGS. 8A-8C are diagrams of communication systems having exemplarylong-term evolution (LTE) and E-UTRA (Evolved Universal TerrestrialRadio Access) architectures, in which the system of FIG. 1 can operateto provide detection of a compatible network, according to variousexemplary embodiments;

FIG. 9 is a diagram of hardware that can be used to implement anembodiment of the invention; and

FIG. 10 is a diagram of exemplary components of a user terminalconfigured to operate in the systems of FIGS. 8A-8C, according to anembodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

An apparatus, method, and software for providing efficient cellre-selection procedure. In the following description, for the purposesof explanation, numerous specific details are set forth in order toprovide a thorough understanding of the embodiments of the invention. Itis apparent, however, to one skilled in the art that the embodiments ofthe invention may be practiced without these specific details or with anequivalent arrangement. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring the embodiments of the invention.

Although the embodiments of the invention are discussed with respect toa wireless network compliant with a 3GPP WCDMA (Wideband Code DivisionMultiple Access) or UTRAN (UMTS (Universal Mobile TelecommunicationsSystem) Terrestrial Radio Access Network)) architecture, it isrecognized by one of ordinary skill in the art that the embodiments ofthe inventions have applicability to any type of packet basedcommunication system and equivalent functional capabilities.

FIG. 1 is a diagram of a communication system capable of providingefficient cell re-selection process, according to an exemplaryembodiment. As shown in FIG. 1, a communication system 100 includes oneor more user equipment (UEs) 101 communicating with a base station 103,which is part of an access network (e.g., WCDMA (Wideband Code DivisionMultiple Access), HSPA (High Speed Packet Access), WiMAX, 3GPP LTE (orE-UTRAN or Beyond 3G, 4G), etc.). The UE 101 can be any type of mobilestations, such as handsets, terminals, stations, units, devices,multimedia tablets, Internet nodes, communicators, Personal DigitalAssistants or any type of interface to the user (such as “wearable”circuitry, etc.). The system 100 provides for notification by a UE 101 ato a current base station 103 within one radio coverage area 105 of theUE's move to another radio coverage area 107 (e.g., cell).Alternatively, according to other embodiments, when resources arededicated to the UE 101 a, the UE 101 a is restricted from performingre-selection of the coverage area 105.

Upon leaving the current coverage area 105, the UE 101 a enters the newcoverage area 107; this movement is depicted as a UE 101 b in thecoverage area 107. Assuming the re-selection process is permissible, theUE 101 b is now served by a new base station 109. Each of the basestations 103, 109 includes a resource allocation logic 103 a, 109 a(respectively) for allocating resources to the UE 101 to communicatewithin the corresponding coverage area 105, 107. In addition, the basestations 103, 109 may include a re-selection logic 103 b, 109 b tooperate in conjunction with the UE 101 to provide the coverage area(e.g., cell) re-selection procedure efficiently, as more fully describedbelow. Likewise, UE 101 has a re-selection logic 111.

In WCDMA, for example, cell re-selection logic may reside elsewhere onthe network side; e.g., such logic can be deployed in the radio networkcontroller (RNC) (or radio resource controller (RRC)). Under the 3GPPterrestrial radio access network architecture (as shown in FIGS. 8A-8C),each of the base stations 103, 109 is denoted as Node B or an enhancedNode B (eNB). The base stations 103, 109, in an exemplary embodiment,use WCDMA (Wideband Code Division Multiple Access) as the uplink anddownlink transmission scheme.

In an exemplary embodiment, the Node B 103, 109 can utilize a hybridAutomatic Repeat Request (ARQ) (HARQ) scheme. Automatic Repeat Request(ARQ) is a retransmission mechanism used on the link layer if thetransmission was not received successfully. HARQ, which combines ARQprotocols with forward-error-correction (FEC) schemes, provides a sounderror-control technique for wireless links. This mechanism permits thereceiver to indicate to the transmitter that a packet or sub-packet hasbeen received incorrectly, and thus, requests the transmitter to resendthe particular packet(s). Further in HARQ technique the receiver canutilize information received with the failed transmission attempt incombination with the retransmission when reconstructing the transmittedpacket

Traditionally, in a cell-re-selection procedure, a UE does not provideany indication to the Node B of current cell about moving to a new cell.UE would simply start a cell update (“CELL_UPDATE”) procedure in the newcell by sending a CELL_UPDATE message on a transport channel (e.g., R'99RACH).

According to certain embodiments, an Enhanced Dedicated Channel (E-DCH)is utilized as a data transmission channel in the CELL_FACH (cellforward access channel) state. E-DCH resources for the UE (resourceshandled by the Node B of the cell UE is connected to) in the cell can beallocated for a relatively long time when comparing to a traditionalCELL_FACH access method using, e.g., at most 20 ms long random accesschannel. During this allocation, the UE may want to change a cell basedon a cell re-selection criteria (e.g., defined by a standard). If the UEutilizes the traditional cell re-selection mechanism, the Node B of thecurrent cell is not notified. Consequently, the UE would change thecell, and the Node B would unnecessarily maintain E-DCH resources ofthis UE.

In recognition of the above problem, the coverage area (e.g., cell)re-selection procedure of system 100 permits the UE 101 to notify thecurrent base station of movement to another coverage area. Twoapproaches are described: FIGS. 2A and 2B present the first approach,and FIG. 3 depicts the second approach.

FIGS. 2A and 2B are flowcharts of a coverage area re-selection processinvolving signaling of movement from a current coverage area to a newcoverage area, according to various exemplary embodiments. By way ofexample, this process is described with respect to the system 100 ofFIG. 1. Under this scenario, the UE 101 communicates with the currentbase station 103 a associated with the coverage area 105, which is thecurrent coverage area. Upon moving to another coverage area 107, whichis served by the new base station 109.

As seen in FIG. 2A, in step 201, the UE 101 a initiates a cellre-selection procedure, which can be triggered by movement into the newcoverage area 107. Thereafter, the UE 101 sends an indication of themove to the current base station 103, per step 203. In other words, whenthe UE 101 has E-DCH resources allocated to it in CELL_FACH state withenhanced uplink in use (i.e., Node B has allocated E-DCH resources) andwhen UE 101 wants to change cell, the UE 101 will indicate to the Node B(e.g., base station 103) of current cell that it plans to release E-DCHresources from the current cell. The Node B 103, as in can thenacknowledge this indication. If the acknowledgement of the indication isreceived (as determined in step 205), a cell update is performed for thenew cell 107.

On the network or base station side (shown in FIG. 2B), the current basestation 103 receives the indication of the move from the UE 101, andappropriately acknowledges (steps 211 and 213). In an exemplaryembodiment, the indication can be sent, for example, in a MAC (MediumAccess Control)-e header to the current Node B 103. Accordingly, thecurrent base station 103 can timely release dedicated resources, as instep 215. In an exemplary embodiment, the dedicated resources (e.g.,E-DCH resources) are immediately released to be available for some otherUE 101. These resources have been previously allocated using theresource allocation logic 103 a within the Node B 103, for instance.

That is, after sending the indication and (optionally) receivingacknowledgement, the UE 101 will release the dedicated resources usedfor transmission and perform CELL_UPDATE into the new cell. Using theabove approach, the current Node B 103 can know when UE 101 wants torelease resources, for example, when UE 101 seeks to change a cell inCELL_FACH state when UE 101 has E-DCH resources in CELL_FACH state.However, it is noted that in a UTRAN system, in order to facilitateinter-frequency or inter-radio access technology measurements,compressed mode or a similar technique would have to be always active inCELL_FACH state because UTRAN has no means to initiate Compressed modewhen UE has E-DCH resources in CELL_FACH state. Intra-frequencymeasurements however, can be performed normally.

FIG. 3 is a flowchart of a process for temporarily disabling a coveragearea re-selection procedure, according to an exemplary embodiment. Instep 301, resources (e.g., E_DCH resources) are allocated to the UE 101.Subsequently, the process detects initiation of cell re-selectionprocedure (step 303), and determines whether resources have beendedicated to the UE 101 (step 305). Per step 307, the process does notpermit execution of the re-selection procedure when the UE 101 has E-DCHresources in CELL_FACH state (e.g., Node B 103 has allocated E-DCHresources). That is, the UE 101 is not allowed to perform cellre-selection as long as it has E-DCH resources reserved. According toone embodiment, the cell re-selection procedure will only occur when theUE 101 does not have a shared E-DCH resource (that has been allocated toit).

After the UE 101 has released (also Node B 103 has released) theresources (as in step 309), the UE 101 can perform cell re-selection(step 311)—e.g., via a traditional cell re-selection logic and using theCELL_UPDATE procedure. In other words, the UE 101 in CELL_FACH statetypically runs its re-selection logic. However, when the UE 101 istransmitting over E-DCH or is running the HS-RACH procedure, in generalthe UE 101 will not perform re-selection until the resources arereleased. This approach would address the inter-frequency andinter-radio access technology measurement problem without a need forintroducing a compressed mode or similar technique.

FIG. 4 is a diagram of an exemplary high speed random access channel(HS-RACH) procedure for supporting cell-re-selection, according tovarious exemplary embodiments. By way of example, a High Speed RandomAccess Channel (HS-RACH) or Fast E-DCH access can be used as a transportchannel in the CELL_FACH (Forward Access Channel) state instead of RACH.The HS-RACH concept is explained as follows. In step 401, determinationof UL interference level for open loop power control is performed. Instep 403, the process involves a random access procedure, R'99 (3GPPR99), with power ramp-up using specific HS-RACH access slots and/orsignatures indicated in a SIB (System Information Block). The processthen, per step 405, performs acquisition indication and resourceassignment.

Next, the start of inner loop power control is performed in the UL 101,e.g., on a DPCCH (Dedicated Physical Control Channel), as in step 407.Also, the process proceeds with the start of inner loop power control inDL, e.g., on F-DPCH (Forward Dedicated Physical Channel (step 409). Atthis point, data transmission on the UL can commence, as in step 411,on, e.g., on E-DPDCH (Enhanced Dedicated Physical Data Channel)/E-DPCCH(Enhanced Dedicated Physical Control Channel). In step 413, a subsequentdata rate grant (update of initial data rate grant) as well as collisiondetection and resolution is executed. Acknowledgement signaling (ACK(Acknowledgement)/NACK (Negative Acknowledgement)) of UL data isprovided on an E-DCH (E-DCH Hybrid ARQ (Automatic Repeat Request)Indicator Channel), per step 415.

Likewise, in step 417, acknowledgement signaling (using ACK/NACK) isperformed for DL data and CQI (Channel Quality Indication) for DL linkadaptation, e.g., on HS-DPCCH. In step 419, the process provides certainmechanisms at the end of data transmission, end of HS-RACH resourceallocation period, collision detection, etc.

To better appreciate the above process, the E-DCH resources are nowdescribed. In Release 99, the RACH channel data rates are very low andthe setup times from CELL_FACH to CELL_DCH are considerable. This leadsto considerable longer delays than needed for medium size packets. UsingHSUPA (High Speed Uplink Packet Access) physical channel in CELL_FACHstate will enhance the data rates in that state considerably. The datatransfer in CELL_FACH with the enhanced data rate can continue, exceptfor a small gap, during the switching to CELL_DCH, thus enabling theuser data transmission to start during the CELL_FACH to CELL_DCH setup,thus hiding from user the fact that the setup takes some time.

The high speed RACH (HS-RACH) concept is illustrated in FIG. 5.

FIG. 5 is a diagram showing usage of Enhanced Dedicated Channel (E-DCH)as a RACH shared channel, according to various exemplary embodiments.Physical channels are utilized as shared channels (or common channels):one or more uplink E-DPDCH and E-DPCCH are used as shared channels(501); and one or more sets of downlink L1 feedback channels are used asshared channels (503). These channels can carry power control (F-DPCH),retransmission requests (ACK/NACK) and capacity allocations (E-AGCH).

FIGS. 6 and 7 are diagrams of simulation results relating to HS-RACHcapacity, according to various exemplary embodiments. HS-RACH capacityis simulated, and graph 600 of FIG. 6 and graph 700 of FIG. 7 providethe results. In these simulations, it is assumed that there are a totalof 2500 uploads per cell per hour. Also, each user is assumed to stay500 ms on HS-RACH before moving to Cell_DCH state. Further, it would bepossible to start the operation with a single HS-RACH and then laterupgrade the capacity according to the traffic needs. The simulationsalso show that if 4 signatures are in place, the collision probabilityis negligible <0.01% with the loading used in the simulations.

By way of example, the described processes and systems can utilize suchnetworks as WCDMA/HSPA, and UMTS terrestrial radio access network(UTRAN), as described below. However, it is recognized that othercommunication architectures can be utilized as well.

FIGS. 8A-8C are diagrams of communication systems having exemplarylong-term evolution (LTE) architectures, in which the user equipment(UE) and the base station of FIG. 1 can operate, according to variousexemplary embodiments. By way of example (shown in FIG. 8A), a basestation (e.g., destination node) and a user equipment (UE) (e.g., sourcenode) can communicate in system 800 using any access scheme, such asTime Division Multiple Access (TDMA), Code Division Multiple Access(CDMA), Wideband Code Division Multiple Access (WCDMA), OrthogonalFrequency Division Multiple Access (OFDMA) or Single Carrier FrequencyDivision Multiple Access (FDMA) (SC-FDMA) or a combination of thereof.In an exemplary embodiment, both uplink and downlink can utilize WCDMA.In another exemplary embodiment, uplink utilizes SC-FDMA, while downlinkutilizes OFDMA. As seen, base stations 103 a-103 n constitute a radionetwork of eNBs as EUTRAN.

The communication system 800 is compliant with 3GPP LTE, entitled “LongTerm Evolution of the 3GPP Radio Technology” (which is incorporatedherein by reference in its entirety). As shown in FIG. 8A, one or moreuser equipment (UEs) communicate with a network equipment, such as abase station 103, which is part of an access network (e.g., WiMAX(Worldwide Interoperability for Microwave Access), 3GPP LTE (orE-UTRAN), etc.). Under the 3GPP LTE architecture, base station 103 isdenoted as an enhanced Node B (eNB).

MME (Mobile Management Entity)/Serving Gateways 801 are connected to theeNBs 103 in a full or partial mesh configuration using tunneling over apacket transport network (e.g., Internet Protocol (IP) network) 803.Exemplary functions of the MME/Serving GW 801 include distribution ofpaging messages to the eNBs 103, termination of U-plane packets forpaging reasons, and switching of U-plane for support of UE mobility.Since the GWs 801 serve as a gateway to external networks, e.g., theInternet or private networks 803, the GWs 801 include an Access,Authorization and Accounting system (AAA) 805 to securely determine theidentity and privileges of a user and to track each user's activities.Namely, the MME Serving Gateway 801 is the key control-node for the LTEaccess-network and is responsible for idle mode UE tracking and pagingprocedure including retransmissions. Also, the MME 801 is involved inthe bearer activation/deactivation process and is responsible forselecting the SGW (Serving Gateway) for a UE at the initial attach andat time of intra-LTE handover involving Core Network (CN) noderelocation.

A more detailed description of the LTE interface is provided in 3GPP TR25.813, entitled “E-UTRA and E-UTRAN: Radio Interface Protocol Aspects,”which is incorporated herein by reference in its entirety.

In FIG. 8B, a communication system 802 supports GERAN (GSM/EDGE radioaccess) 804, and UTRAN 806 based access networks, E-UTRAN 812 andnon-3GPP (not shown) based access networks, and is more fully describedin TR 23.882, which is incorporated herein by reference in its entirety.A key feature of this system is the separation of the network entitythat performs control-plane functionality (MME 808) from the networkentity that performs bearer-plane functionality (Serving Gateway 810)with a well defined open interface between them S11. Since E-UTRAN 812provides higher bandwidths to enable new services as well as to improveexisting ones, separation of MME 808 from Serving Gateway 810 impliesthat Serving Gateway 810 can be based on a platform optimized forsignaling transactions. This scheme enables selection of morecost-effective platforms for, as well as independent scaling of, each ofthese two elements. Service providers can also select optimizedtopological locations of Serving Gateways 810 within the networkindependent of the locations of MMEs 808 in order to reduce optimizedbandwidth latencies and avoid concentrated points of failure.

As seen in FIG. 8B, the E-UTRAN (e.g., eNB) 812 interfaces with UE 101via LTE-Uu. The E-UTRAN 812 supports LTE air interface and includesfunctions for radio resource control (RRC) functionality correspondingto the control plane MME 808. The E-UTRAN 812 also performs a variety offunctions including radio resource management, admission control,scheduling, enforcement of negotiated uplink (UL) QoS (Quality ofService), cell information broadcast, ciphering/deciphering of user,compression/decompression of downlink and uplink user plane packetheaders and Packet Data Convergence Protocol (PDCP).

The MME 808, as a key control node, is responsible for managing mobilityUE identifies and security parameters and paging procedure includingretransmissions. The MME 808 is involved in the beareractivation/deactivation process and is also responsible for choosingServing Gateway 810 for the UE 101. MME 808 functions include Non AccessStratum (NAS) signaling and related security. MME 808 checks theauthorization of the UE 101 to camp on the service provider's PublicLand Mobile Network (PLMN) and enforces UE 101 roaming restrictions. TheMME 808 also provides the control plane function for mobility betweenLTE and 2G/3G access networks with the S3 interface terminating at theMME 808 from the SGSN (Serving GPRS Support Node) 814.

The SGSN 814 is responsible for the delivery of data packets from and tothe mobile stations within its geographical service area. Its tasksinclude packet routing and transfer, mobility management, logical linkmanagement, and authentication and charging functions. The S6a interfaceenables transfer of subscription and authentication data forauthenticating/authorizing user access to the evolved system (AAAinterface) between MME 808 and HSS (Home Subscriber Server) 816. The S10interface between MMEs 808 provides MME relocation and MME 808 to MME808 information transfer. The Serving Gateway 810 is the node thatterminates the interface towards the E-UTRAN 812 via S1-U.

The S1-U interface provides a per bearer user plane tunneling betweenthe E-UTRAN 812 and Serving Gateway 810. It contains support for pathswitching during handover between eNBs 103. The S4 interface providesthe user plane with related control and mobility support between SGSN814 and the 3GPP Anchor function of Serving Gateway 810.

The S6 is an interface between UTRAN 806 and Serving Gateway 810. PacketData Network (PDN) Gateway 818 provides connectivity to the UE 101 toexternal packet data networks, (e.g. Internet or Intranet) by being thepoint of exit and entry of Internet traffic for the UE 101. The PDNGateway 818 performs policy enforcement, packet filtering for each user,charging support, lawful interception and packet screening. Another roleof the PDN Gateway 818 is to act as the anchor for mobility between 3GPPand non-3GPP technologies such as WiMax and 3GPP2 (CDMA 1× and EvDO(Evolution Data Only)).

The S7 interface provides transfer of QoS policy and charging rules fromPCRF (Policy and Charging Role Function) 820 to Policy and ChargingEnforcement Function (PCEF) in the PDN Gateway 818. The SGi interface isthe interface between the PDN Gateway and the operator's IP servicesincluding packet data network 822. Packet data network 822 may be anoperator external public or private packet data network or an intraoperator packet data network, e.g., for provision of IMS (IP MultimediaSubsystem) services. Rx+ is the interface between the PCRF and thepacket data network 822.

As seen in FIG. 8C, the eNB 103 utilizes an E-UTRA (Evolved UniversalTerrestrial Radio Access) (user plane, e.g., RLC (Radio Link Control)815, MAC (Media Access Control) 817, and PHY (Physical) 819, as well asa control plane (e.g., RRC 821)). These functions are also providedwithin the UE 101. The eNB 103 also includes the following functions:Inter Cell RRM (Radio Resource Management) 823, Connection MobilityControl 825, RB (Radio Bearer) Control 827, Radio Admission Control 829,eNB Measurement Configuration and Provision 831, and Dynamic ResourceAllocation (Scheduler) 833.

The eNB 103 communicates with the aGW 801 (Access Gateway) via an S1interface. The aGW 801 includes a Control plane 801 a and a User Plane801 b. aGW is a conceptual notation inclusive of MME in the controlplane and PDN/serving gateways in the user plane. Evolve Packet Core isthe core network architecture that in addition to MME and PDN/servinggateways consists of server architecture e.g. for Internet MultimediaSubsystem (IMS).

The user plane 801 b includes PDN/Serving gateway functionalities 845,e.g. management of PDP context (Packet Data Protocol context) 840, and aUser plane Mobility Anchoring function 847. It is noted that thefunctionality of the aGW 801 can also be provided by a combination of aserving gateway (SGW) and a packet data network (PDN) GW. The aGW 801can also interface with a packet network, such as the Internet 843. PDP(Packet Data protocol) context defines the IP connectivity parameterse.g. QoS.

The control plane 801 b provides the following components as theMobility Management Entity (MME): SAE (System Architecture Evolution)Bearer Control 851, Idle State Mobility Handling 853, and NAS(Non-Access Stratum) Security 855.

One of ordinary skill in the art would recognize that the processes forcoverage area re-selection may be implemented via software, hardware(e.g., general processor, Digital Signal Processing (DSP) chip, anApplication Specific Integrated Circuit (ASIC), Field Programmable GateArrays (FPGAs), etc.), firmware, or a combination thereof. Suchexemplary hardware for performing the described functions is detailedbelow with respect to FIG. 9.

FIG. 9 illustrates exemplary hardware upon which various embodiments ofthe invention can be implemented. A computing system 900 includes a bus901 or other communication mechanism for communicating information and aprocessor 903 coupled to the bus 901 for processing information. Thecomputing system 900 also includes main memory 905, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to the bus901 for storing information and instructions to be executed by theprocessor 903. Main memory 905 can also be used for storing temporaryvariables or other intermediate information during execution ofinstructions by the processor 903. The computing system 900 may furtherinclude a read only memory (ROM) 907 or other static storage devicecoupled to the bus 901 for storing static information and instructionsfor the processor 903. A storage device 909, such as a magnetic disk oroptical disk, is coupled to the bus 901 for persistently storinginformation and instructions.

The computing system 900 may be coupled via the bus 901 to a display911, such as a liquid crystal display, or active matrix display, fordisplaying information to a user. An input device 913, such as akeyboard including alphanumeric and other keys, may be coupled to thebus 901 for communicating information and command selections to theprocessor 903. The input device 913 can include a cursor control, suchas a mouse, a trackball, or cursor direction keys, for communicatingdirection information and command selections to the processor 903 andfor controlling cursor movement on the display 911.

According to various embodiments of the invention, the processesdescribed herein can be provided by the computing system 900 in responseto the processor 903 executing an arrangement of instructions containedin main memory 905. Such instructions can be read into main memory 905from another computer-readable medium, such as the storage device 909.Execution of the arrangement of instructions contained in main memory905 causes the processor 903 to perform the process steps describedherein. One or more processors in a multi-processing arrangement mayalso be employed to execute the instructions contained in main memory905. In alternative embodiments, hard-wired circuitry may be used inplace of or in combination with software instructions to implement theembodiment of the invention. In another example, reconfigurable hardwaresuch as Field Programmable Gate Arrays (FPGAs) can be used, in which thefunctionality and connection topology of its logic gates arecustomizable at run-time, typically by programming memory look uptables. Thus, embodiments of the invention are not limited to anyspecific combination of hardware circuitry and software.

The computing system 900 also includes at least one communicationinterface 915 coupled to bus 901. The communication interface 915provides a two-way data communication coupling to a network link (notshown). The communication interface 915 sends and receives electrical,electromagnetic, or optical signals that carry digital data streamsrepresenting various types of information. Further, the communicationinterface 915 can include peripheral interface devices, such as aUniversal Serial Bus (USB) interface, a PCMCIA (Personal Computer MemoryCard International Association) interface, etc.

The processor 903 may execute the transmitted code while being receivedand/or store the code in the storage device 909, or other non-volatilestorage for later execution. In this manner, the computing system 900may obtain application code in the form of a carrier wave.

The term “computer-readable medium” as used herein refers to any mediumthat participates in providing instructions to the processor 903 forexecution. Such a medium may take many forms, including but not limitedto non-volatile media, volatile media, and transmission media.Non-volatile media include, for example, optical or magnetic disks, suchas the storage device 909. Volatile media include dynamic memory, suchas main memory 905. Transmission media include coaxial cables, copperwire and fiber optics, including the wires that comprise the bus 901.Transmission media can also take the form of acoustic, optical, orelectromagnetic waves, such as those generated during radio frequency(RF) and infrared (IR) data communications. Common forms ofcomputer-readable media include, for example, a floppy disk, a flexibledisk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM,CDRW, DVD, any other optical medium, punch cards, paper tape, opticalmark sheets, any other physical medium with patterns of holes or otheroptically recognizable indicia, a RAM, a PROM, and EPROM, a FLASH-EPROM,any other memory chip or cartridge, a carrier wave, or any other mediumfrom which a computer can read.

Various forms of computer-readable media may be involved in providinginstructions to a processor for execution. For example, the instructionsfor carrying out at least part of the invention may initially be borneon a magnetic disk of a remote computer. In such a scenario, the remotecomputer loads the instructions into main memory and sends theinstructions over a telephone line using a modem. A modem of a localsystem receives the data on the telephone line and uses an infraredtransmitter to convert the data to an infrared signal and transmit theinfrared signal to a portable computing device, such as a personaldigital assistant (PDA) or a laptop. An infrared detector on theportable computing device receives the information and instructionsborne by the infrared signal and places the data on a bus. The busconveys the data to main memory, from which a processor retrieves andexecutes the instructions. The instructions received by main memory canoptionally be stored on storage device either before or after executionby processor.

FIG. 10 is a diagram of exemplary components of a user terminalconfigured to operate in the systems of FIGS. 8A-8C, according to anembodiment of the invention. A user terminal 1000 includes an antennasystem 1001 (which can utilize multiple antennas) to receive andtransmit signals. The antenna system 1001 is coupled to radio circuitry1003, which includes multiple transmitters 1005 and receivers 1007. Theradio circuitry encompasses all of the Radio Frequency (RF) circuitry aswell as base-band processing circuitry. As shown, layer-1 (L1) andlayer-2 (L2) processing are provided by units 1009 and 1011,respectively. Optionally, layer-3 functions can be provided (not shown).L2 unit 1011 can include module 1013, which executes all Medium AccessControl (MAC) layer functions. A timing and calibration module 1015maintains proper timing by interfacing, for example, an external timingreference (not shown). Additionally, a processor 1017 is included. Underthis scenario, the user terminal 1000 communicates with a computingdevice 1019, which can be a personal computer, work station, a PersonalDigital Assistant (PDA), web appliance, cellular phone, etc.

While the invention has been described in connection with a number ofembodiments and implementations, the invention is not so limited butcovers various obvious modifications and equivalent arrangements, whichfall within the purview of the appended claims. Although features of theinvention are expressed in certain combinations among the claims, it iscontemplated that these features can be arranged in any combination andorder.

What is claimed is:
 1. A method comprising: generating, by a userequipment, a notification message indicating initiation of a coveragearea re-selection procedure to operate in a new coverage area from acurrent coverage area; determining to transmit the notification messageto a current base station serving the current coverage area; andperforming, by the user equipment, the re-selection procedure inresponse to the transmission of the notification message, wherein thenotification message is triggered based on detection of movement of theuser equipment into the new coverage area, the notification messagebeing sent to the current base station that serves the current coveragearea.
 2. The method according to claim 1, further comprising: receivingan acknowledgement message to perform the re-selection procedure.
 3. Themethod according to claim 2, wherein the current base station isconfigured to release dedicated resources of a transport channel withinthe current coverage area in response to the notification message, andthe coverage area re-selection procedure is temporarily disabled at theuser equipment until the release of the dedicated resources.
 4. Themethod according to claim 1, wherein the notification message istransmitted in a Medium Access Control (MAC)-e header.
 5. An apparatuscomprising: at least one processor; and at least one memory includingcomputer program code for one or more programs, the at least one memoryand the computer program code configured to, with the at least oneprocessor, cause the apparatus to perform at least the following,generate a notification message indicating initiation of a coverage areare-selection procedure for a user equipment to operate in a new coveragearea from a current coverage area, determine to transmit thenotification message to a current base station serving the currentcoverage area, and perform the re-selection procedure in response to thetransmission of the notification message, wherein the apparatus isincluded in the user equipment, and wherein the notification message istriggered based on detection of movement of the user equipment into thenew coverage area, the notification message being sent to the currentbase station that serves the current coverage area.
 6. The apparatusaccording to claim 5, wherein the apparatus is further caused to:receive an acknowledgement message to perform the re-selectionprocedure.
 7. The apparatus according to claim 6, wherein the currentbase station is configured to release dedicated resources of a transportchannel within the current coverage area in response to the notificationmessage, and the coverage area re-selection procedure is temporarilydisabled at the user equipment until the release of the dedicatedresources.
 8. A method comprising: receiving, at a current base stationserving a current coverage area, a notification message from a userequipment, the notification message indicating initiation of a coveragearea re-selection procedure to operate in a new coverage area from thecurrent coverage area; and generating, at the current base station, anacknowledgement message to permit executing the re-selection procedurein response to the reception of the notification message, wherein thenotification message is triggered based on detection of movement of theuser equipment into the new coverage area.
 9. The method according toclaim 8, further comprising: releasing from the user equipment dedicatedresources of a transport channel within the current coverage area inresponse to the notification message.
 10. The method according to claim9, further comprising: temporarily disabling the coverage areare-selection procedure because of the existence of the dedicatedresources.
 11. The method according to claim 9, wherein the coverageareas are associated with a cellular network, and the transport channelis a high speed random access channel (HS-RACH) or an enhanced dedicatedchannel (E-DCH).
 12. An apparatus comprising: at least one processor;and at least one memory including computer program code for one or moreprograms, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatus toperform at least the following, receive, at a current base stationserving a current coverage area, a notification message from a userequipment, the notification message indicating initiation of a coveragearea re-selection procedure for the user equipment to operate in a newcoverage area from the current coverage area, and generate anacknowledgement message to permit executing the re-selection procedurein response to the reception of the notification message, and whereinthe notification message is triggered based on detection of movement ofthe user equipment into the new coverage area.
 13. The apparatusaccording to claim 12, wherein the current base station is configured torelease from the user equipment dedicated resources of a transportchannel within the current coverage area in response to the notificationmessage, and the coverage area re-selection procedure is temporarilydisabled because of the existence of the dedicated resources.
 14. Themethod comprising: determining, by a user equipment, whether a coveragearea re-selection state exists; initiating, by the user equipment,execution of a coverage area re-selection procedure based on thedetermination that the coverage area re-selection state exists and whena transmission resource is not currently allocated to the userequipment; and generating, by the user equipment, a notification messageindicating the initiation of the coverage area re-selection procedure tooperate in a new coverage area from a current coverage area, wherein thenotification message is triggered based on detection of movement of theuser equipment into the new coverage area, the notification messagebeing sent to the current base station that serves the current coveragearea.
 15. The method according to claim 14, further comprising:releasing, by the user equipment, the transmission resource.
 16. Themethod according to claim 15, further comprising: executing, by the userequipment, the coverage area re-selection procedure after the release ofthe transmission resource.
 17. The method according to claim 14, furthercomprising: receiving, by the user equipment, an acknowledgement messageto perform the re-selection procedure.
 18. The method according to claim14, wherein the transmission resource is associated with either a highspeed random access channel (HS-RACH) or an enhanced dedicated channel(E-DCH).
 19. The method according to claim 14, wherein the coverage areare-selection procedure is temporarily disabled because of the allocationof the transmission resource.
 20. An apparatus comprising: at least oneprocessor; and at least one memory including computer program code forone or more programs, the at least one memory and the computer programcode configured to, with the at least one processor, cause the apparatusto perform at least the following, determine whether a coverage areare-selection state exists for a user equipment, initiate execution of acoverage area re-selection procedure at the user equipment based on thedetermination that the coverage area re-selection state exists and whena transmission resource is not currently allocated to the userequipment, and generate a notification message indicating the initiationof the coverage area re-selection procedure for the user equipment tooperate in a new coverage area from a current coverage area, wherein thenotification message is triggered based on detection of movement of theuser equipment into the new coverage area, the notification messagebeing sent to the current base station that serves the current coveragearea, and wherein the apparatus is included in the user equipment. 21.The apparatus according to claim 20, wherein the apparatus is furthercaused to: release the transmission resource.
 22. The apparatusaccording to claim 21, wherein the apparatus is further caused to:execute the coverage area re-selection procedure after the release ofthe transmission resource.
 23. The apparatus according to claim 20,wherein the apparatus is further caused to: initiate transmission of thenotification message from the user equipment to a current base stationserving the current coverage area, and receive an acknowledgementmessage at the user equipment to perform the re-selection procedure. 24.The apparatus according to claim 20, wherein the transmission resourceis associated with either a high speed random access channel (HS-RACH)or an enhanced dedicated channel (E-DCH).
 25. The apparatus according toclaim 20, wherein the coverage area re-selection procedure istemporarily disabled because of the allocation of the transmissionresource.